Published online by Cambridge University Press: 04 July 2016
The experimental methods in current use for the determination of the dynamic properties of an arbitrary finite-freedom system are based on restrictive assumptions which may often be of questionable validity. The most common assumption is that the damping matrix can be reduced to a diagonal form by a congruent transformation using the modal matrix of the undamped system. Further, the damping is normally assumed to be hysteretic, or light if viscous.
Bishop and Gladwell give an excellent account of the theoretical background of the present experimental techniques. These can be divided into three groups:
1. The method of Kennedy and Pancu which obtains experimentally the complex receptance of the system and extracts its dynamic properties from vectorial plots.
2. The method of Trail-Nash and Asher which is based on the experimental determination of the in-phase response of the system and requires computation to be incorporated with the experimental procedure.